Apologies for necroing an old thread, but I thought I'd add that according to the dosbox documentation found at
https://www.dosbox.com/wiki/Performance#Emulated_CPU_equivalency "fixed 315" is a pretty good clock cycle to use. It is a pretty close equivalent to what an 8088/8086 from the IBM Personal Computers of the time would have been running the game at.
I didn't find the patch to be sufficient, but with a fixed clock cycle of 315, the key delay feels mostly snappy with a small delay actually being useful for points in the game where you're turning in complete darkness and text speed is pretty nice with the text crawl in the demo being readable with minimal speed reading.
Edit: I was having some issues where the game would only refresh the screen partially. I'm not sure if it's connected to the low cycle rate or the high resolution graphics mod, but I believe I've fixed it by fulldouble=true in the .conf file. I'll need to do further testing to verify.